GlobalSign Blog

11 Aug 2017

What is Certificate Transparency?

Certificate Transparency (CT) probably first came on your radar a few years ago when Google announced it as a requirement for all Extended Validation (EV) SSL/TLS Certificates issued after 1 Jan 2015. Since then, Google has expanded the requirement to cover all types of SSL Certificates and most recently announced a deadline of April 2018. Certificates issued after that date that are not CT qualified will not be trusted in Chrome.

At GlobalSign, we’ve been working hard behind the scenes to equip all of our certificates with CT – Extended Validation (EV) since 2015, Domain Validated (DV) since August 2016 and Organization Validated (OV) is coming in October 2017 - so our customers will be ready for Google’s deadline next year.

In the meantime, for those of you who are still wondering what CT is all about, consider this your prep course.

Note: For the sake of simplicity, we’re using the term SSL instead of TLS throughout this post (with one exception) since it’s more commonly used. For more on this, read our related post.

What is Certificate Transparency?

Certificate Transparency is an open framework for monitoring SSL Certificates. Domain owners may find it useful to monitor certificate issuance for their domain and use that to detect misissued certificates. Prior to CT, there was not an efficient way to get a comprehensive list of certificates issued to your domain.

With CT, all certificates are publicly disclosed, providing greater insight and transparency into the Web PKI ecosystem as a whole. The Certificate Transparency Project aims to achieve three goals:

To make it impossible (or at least very difficult) for a CA to issue a SSL Certificate for a domain without the certificate being visible to the owner of that domain.

To provide an open auditing and monitoring system that lets any domain owner or CA determine whether certificates have been mistakenly or maliciously issued.

To protect users from being duped by certificates that were mistakenly or maliciously issued.

The Certificate Transparency framework means misissued certificates can be detected quickly and efficiently as compared to the old system where rogue certificates could be left in the wild to wreak havoc for weeks or months before being discovered. Early detection of suspect certificates allows CAs and domain owners alike to act quickly and revoke the certificates.

How Certificate Transparency Works

The main two CT components are the CT logs and Monitors.

CT logs maintain records of issued SSL Certificates. These logs are append-only, meaning entries can’t be deleted or altered in any way once a certificate has been added to a log. SSL Certificates and precertificates (more on this below) may be posted to CT logs. Upon receipt of a valid SSL Certificate or precertificate, the log returns a Signed Certificate Timestamp (SCT), which is proof that the log received the request. CT logs use a cryptographic mechanism called Merkle Tree Hash that prevents log entries from being modified or deleted, so once posted they are always visible to the public. Browsers may require SCTs (which indicate that the certificate was publicly disclosed) while processing SSL Certificates when establishing a TLS session, so these SCTs are an increasingly important feature in the Web PKI. More on this later.

Monitors query CT logs and can download and store certificates for subsequent reporting. Monitors will parse the certificates into subfields and allow their users to create and run queries for certificates. Domain owners may be interested receiving notices for certificates issued to their domains, or for certificates that match their Organizational name, while compliance teams may be looking for compliance with the CA/Browser Forum Baseline Requirements or Root Program requirements. Regardless, there are many purposes for Monitors. Some third party services have released CT Monitoring tools or started bundling them into their existing solution packages. For example, Facebook launched a free monitoring service of their own at the end of last year.

What Are Precertificates?

As mentioned above, CT logs accept SSL precertificates and certificates. A precertificate contains all the same data as the “real” certificate, but also contains one additional extension that makes the certificate unusable. This extension is referred to as a poison extension and is used to distinguish it from the “real” certificate. Since all certificates issued by a CA must contain unique serial numbers, and since both the precertificate and certificate will have the same serial number, it’s important to make one of them as invalid or not usable, thus the poison extension.

Why Are Precertificates Useful?

There are several methods for delivering SCTs to browsers for processing, but the most reliable and useful is by including SCTs into the certificate. In order to obtain SCTs prior to issuance (so they can be included into the certificate), the CA must create a precertificate, post it to CT logs, receive SCTs and then include them into the final certificate.

Prior to issuing a certificate, a CA may submit a precertificate to CT logs as intent to issue the corresponding certificate. In fact, creating and posting a precertificate that is not properly validated or formatted is considered a misissuance.

Who Can Submit Certificates to CT logs?

Anyone can submit certificates to CT logs, but only CAs will submit precertificates. Search engines and website operators also often post certificates to CT logs.

Some CT log operators accept certificates under only certain roots, some don’t accept expired certificates, and all certificates (or precertificates) must be intended to be used as SSL Certificates (i.e. you cannot post S/MIME or Code Signing Certificates to CT logs).

Using SCTs

The SCT – the proof that the certificate has been logged - must be made available to the web browser in order for the browser to properly evaluate the SSL Certificate. The exact browser behavior and requirements for SCTs varies by browser, but in all cases, the browser must receive the SCTs. While the browser could theoretically post SSL Certificates to logs when creating a TLS session to get SCTs, the overhead in doing so would be prohibitive. There are three main methods for delivering SCTs to the browser:

1. Certificate Extension

The most common and the most reliable method for delivering SCTs to the browser is for the CA to include SCTs into the certificate. Since the browser needs the SSL Certificate to establish the TLS session, the certificate is guaranteed to be present and can always be used for reading SCTs.

Some website owners may not want to make their website URLs known prior to launching their site, so they may not want to post their certificates to CT logs in advance. In this case, one of the other delivery options may be preferred.

2. TLS (SSL) Extension

The website operator may provide SCTs to the browser within the TLS protocol. In this model, the website operator/webserver submits the certificate to CT logs and obtains the SCTs. The SCTs are included in the TLS handshake via a TLS extension called “signed_certificate_timestamp”. The “downside” to this delivery method is that webserver operators must change their default webserver configurations and not all webservers support this option.

3. OCSP Stapling

OCSP messages may be used for the distribution of SCTs to the browser. Two items are needed to support this method:

The website operator must use a webserver that supports OCSP stapling and must configure their server to request and download a valid OCSP response. If this is not done, there is no guarantee that the browser will go fetch the OCSP message containing the SCTs (many browsers do not support OCSP, so this is not a reliable delivery mechanism unless the OCSP response is include in the TLS protocol).

The CA must configure their OCSP service to support SCT stapling. After the certificate has been issued, the CA will post it to multiple logs and receive SCTs. When OCSP responses are generated, the CA will attach the SCTs to the OCSP message and then the browser will have both the revocation status and the necessary SCTs.

While both methods 2 and 3 require special server configuration, they can offer more flexibility compared to option 1 above if certificate logs become untrusted since the web site operator and CA can more dynamically reconfigure the logs being used.

The Google CT Policy

In order to be “CT qualified”, Google requires a certificate to appear in multiple logs (at least one Google log and one non-Google log) and the number of SCTs needed depends on the validity period of the certificate. For more details, please see Google’s Certificate Transparency in Chrome.

So What Do You Need to Do to Be CT Compliant?

Well, now you know the basics of CT! The best solution to make sure you’re compliant is to select a CA that adds SCTs to issued certificate in compliance with the Google CT policy. The vast majority of GlobalSign SSL Certificates already comply with the Google policy and in a few months all certificates will comply, a full 5 months prior to the Google deadline of April, 2018.

So far, Google has been the only browser to announce timelines for requiring CT. Mozilla has drafted a policy, but no dates have been announced yet and we expect their requirements to be compatible with the Google requirements. You can follow the discussion here. We will update this post pending any future announcements.

Have questions about certificate transparency and whether your certificates are compliant? Contact us anytime; we’re happy to help.

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GlobalSign respects your right to privacy.This privacy policy has been developed to inform you about the privacy practices followed by GlobalSign in connection with its websites, products and services. This privacy policy does not apply to GlobalSign services offered by or through our partners, resellers or other third parties, or other third party services or websites, and we encourage you to read the privacy policies of those parties.

This privacy policy will inform you about what data is collected, how we use such data, where data is processed, how you may opt out of your data being used, the security provisions around storing your data and how to correct or update your data.

1. Data Controller

In order to communicate with you and to provide our products and services and related support, it is necessary for GlobalSign to transfer your personal data outside of the European Union. In such case, the data controller for this data for EU residents is GMO GlobalSign, Ltd., having its registered offices at Springfield House, Sandling Road, Maidstone, Kent, ME14 2LP, United Kingdom. All questions or requests regarding the processing of data may be addressed to: dpo@globalsign.com.

2. Collection of Personal Information

We collect information from you when you (i) place an order for a GlobalSign digital certificate product or other product or service, (ii) scan your servers for digital certificates using our Certificate Inventory Tool (CIT), (iii) apply for access to our managed service platforms, (iv) subscribe to our newsletter, (v) use our online chat service, (vi) download a white paper, (vii) register for a webinar, (viii) respond to a survey, (ix) fill out a form for pre/post sales assistance, (x) open a support ticket, or (xi) your use of social media.

GlobalSign is a Certification Authority and trusted third party. To fulfill requests for digital certificates or other products or services, you may be asked to enter your name, email address, physical address, phone number, credit card information and/or organizational details or other personal information.

We may develop and acquire additional information about you using third-party sources, browsing, and purchasing history, and so on in order to process certificate requests and to improve our services.

GlobalSign treats personal information as confidential, except for the information included in an issued digital certificate. Such information may be verified using third party commercial and government resources, and as such, is deemed to be public information.

3. Use of Personal Information

Your information, whether public or private, will not be sold, exchanged, transferred outside of our group company, or given to any other company for any reason without your consent, other than for the purposes specified in below:

3.1 To process applications for GlobalSign products and services

Your information is used to provide our products and services and order processing as well as to conduct business transactions such as billing.

The email address you provide for order processing may be used to send you renewal notices for your expiring digital certificate.

3.4 To send periodic emails

In addition, we may send you periodic company newsletters, new service updates, security updates, related product or service information, and status updates on maintenance windows or service availability.

3.5 To tell you about our products and services

We may send you information about our products and services that may be of interest to you based on your use of other GlobalSign products and services, your attendance at GlobalSign sponsored marketing events such as webinars, your requests for information about similar products and services, or your sharing of data with social media sites such as LinkedIn or Facebook.

4. Processing of Data and Consent

We will process your data for the purpose of performance of our contract with you or the legitimate interest of our business. In other cases, we will request your consent for the processing of the personal data you may submit.

Your refusal to provide personal data to us for certain products and services may hinder us from fulfilling your order for those products or services. Also, if you deny or withdraw your consent to use personal data or opt out of receiving information about GlobalSign products and services this may result in you not being made aware of sales promotions, renewal notices, periodic company newsletters, new service updates, security updates, related product or service information, and status updates on maintenance windows or service availability.

5. Use of Cookies and web beacons

The GlobalSign Certificate Center (GCC) uses cookies to enable the fulfillment of services. Cookies may be used when you log into the GCC, purchase products or use certain GCC functions.

In addition, like most online businesses, GlobalSign uses cookies and web beacons on our websites and through marketing related emails to gather and analyze some personal data such as the visitor’s IP address, browser type, ISP, referring page, operating system, date/time and basic geographical information.

We use cookies and web beacons to compile aggregate data about site traffic and site interaction so that we can gauge the effectiveness of our communications and offer better site experiences and tools in the future. We may contract with third-party service providers to assist us in better understanding our site visitors. These service providers are not permitted to use the information collected on our behalf except to help us conduct and improve our business.

First time visitors may choose to not have any activity monitoring cookies set in their browser. We use an opt-out identification cookie to tag these users as having made this decision. Those cookies that pertain to site performance, experience improvement and marketing are programmed not to execute when an opt-out cookie is present in a visitor’s browser. Opt-out cookies persist until a visitor clears their browser cookies, or until their expiration one year after the set date. A visitor is required to opt out again after one year in order to disable any activity monitoring cookies.

6. Use of application logs for diagnostics or to gather statistical information

Our servers automatically record information ("Application Log Data") created by your use of our services. Application Log Data may include information such as your IP address, browser type, operating system, the referring web page, pages visited, location, your mobile carrier, device and application IDs, search terms, and cookie information. We use this information to diagnose and improve our services. Except as stated in section 8 (Data Retention), we will either delete the Application Log Data or remove any account identifiers, such as your username, full IP address, or email address, after 12 months.

7. Sharing of Information and Transfers of Data

We do not sell or trade your personal information to outside parties.

GlobalSign is a global organization with business processes and technical systems in various countries. As such, we may share information about you within our group company and transfer it to countries in the world where we do business in connection with the uses identified in section 3 above and in accordance with this Privacy Policy. In these cases, personal data will be transferred to countries that do not provide an adequate level of protection under European law so we ensure your data is protected by entering into agreements containing standard contract clauses with each of our group companies a copy of which may be obtained by contacting us as outlined in section 15 below.

We may also transfer your personal data to trusted third parties in order to serve purposes that are specified in section 3 above. In circumstances where data is shared with such third parties, they are required to agree to confidentiality terms. This prohibits such third parties from selling, trading, using, marketing or otherwise distributing GlobalSign customer data.

We may also release your information when we believe release is appropriate to comply with the law or protect our rights, property, or safety.

It is our policy to notify customers of requests for their data from law enforcement unless we are prohibited from doing so by statute or court order. Law enforcement officials who believe that notification would jeopardize an investigation should obtain an appropriate court order or other process that specifically precludes member notification, such as an order issued pursuant to 18 U.S.C. §2705(b).

We may also disclose your personal information to third parties who may take over the operation of our site or who may purchase any or all of our assets, including your personal information. We will contact you using the details you provide if there is any change in the person controlling your information.

8. Data retention

The personal information we collect is retained for no longer than necessary to fulfil the stated purposes in section 2 above or for a period specifically required by law or regulation that GlobalSign is obligated to follow.

To meet public CA audit requirements as detailed in the GlobalSign Certification Practice Statement, personal data used to fulfill verification of certain types of digital certificate applications will be retained for a minimum of 10 years depending on the class of product or service and may be retained in either a physical or electronic format. Please refer to the GlobalSign Certification Practice Statement for full details.

Even if you request deletion or erasure of your data, we may retain your personal data to the extent necessary and for so long as necessary for our legitimate business interests or performance of contractual obligations.

After the retention period is over, GlobalSign securely disposes or anonymizes your personal information in order to prevent loss, theft, misuse, or unauthorized access.

9. Opting out; withdrawing consent

If at any time you would like to unsubscribe from receiving future emails, we include unsubscribe instructions at the bottom of each email.

Renewal notices may be cancelled on a per digital certificate basis by logging into your GlobalSign Certificate Center (GCC) account and disabling renewal notices.

Email preferences for CIT related/collected information can be updated and changed within CIT.

If GlobalSign is processing your personal data based on your consent, you may withdraw your consent at any time by contacting us at one of the addresses shown in section 15 below.

10. Acess to your personal data

You are responsible for providing Globalsign with true, accurate, current and complete personal information. Also you are responsible to maintain and promptly update the information to keep it true, accurate, current and complete.

You have the right to access and modify your personal data stored on GlobalSign systems.

You can request to access or modify your personal information by contacting us in writing. We will require you to provide identification in order to verify the authenticity as the data subject. We will make reasonable effort to respond to and process your request in a timely manner.

If you provide any information that is untrue, inaccurate, not current or incomplete, or if we have reasonable grounds to suspect that such information is untrue, inaccurate, not current or incomplete, we have the right to suspend or terminate your account and refuse any and all current or future services.

11. How we protect your information

We implement a variety of security measures to maintain the safety of your personal information when you place an order or enter, submit, or access your personal information. All supplied sensitive/credit information is transmitted via Secure Socket Layer (SSL).

After a transaction, your transaction-related information will be kept on file to meet audit requirements and facilitate renewals. We do not retain any credit card details.

GlobalSign uses a reputable third party to process credit card payments and needs to provide credit card numbers and identifying financial data directly to the third party credit card processor. Such information is shared securely.

12. Follow relevant laws

GlobalSign commits itself to protect the personal information submitted by applicants and subscribers for its public certification services. GlobalSign declares to fully respect all rights established and laid out in European laws and operates within the limits of the:

European Directive 95/46 on the protection of individuals with regard to the processing of personal data and on the free movement of such data; and

Provisions of the GlobalSign CPS.

13. Your rights

In compliance with the European Union rules on privacy, you have the following rights established by law:

We use the data you submit only for purposes identified in section 3 of this privacy policy.

You have the right to review your personal data that GlobalSign holds and check it for accuracy.

You have the right to correct data in the case that errors may be found in our records.

You have the right to request that any of your personal data be erased. i.e. right to be forgotten.

You have the right to obtain and reuse use your personal data for your own purposes

You have the right to request that GlobalSign restrict the processing of your personal data under certain circumstances.

You have the right to object to our processing of your personal data.

14. Changes to our Privacy Policy

If we make material changes to our privacy policy, we will inform customers by emailing a notice of the availability of a new version with a link to the new version.

15. Contact Us

If you have any inquires, or questions regarding our privacy policy, please contact us at:

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GlobalSign is the leading provider of trusted identity and security solutions enabling businesses, large enterprises, cloud service providers and IoT innovators around the world to secure online communications, manage millions of verified digital identities and automate authentication and encryption. Its high-scale Public Key Infrastructure (PKI) and identity solutions support the billions of services, devices, people and things comprising the Internet of Everything (IoE).